I cant say much, but one of the methods is a very simple one – by mails. Lets say you have 3TBs of data that need to get transferred. Just shove it to a disk drive and ship it across the globe. Nobody will notice and if somebody stumbles into one, its garbage because you can encrypt it. A more “express” derivative of this method is shipping via diplomatic channel, nobody can touch your goods. It beats your average internet speed by a lot. But you need to have operatives does the dirty work directly, not just sitting in a basement half across the world.